Liquid coupling for doppler sonic flowmeter

Abstract

A coupling device for attachment of a sonic doppler flowmeter to pipes or conduits is shown and described. In this coupling, a temperature compensated liquid wedge is used to couple the transducer to the wall of the pipe or conduit, and means are shown and described for eliminating bubbles from the liquid wedge region.

What is claimed is: 
     
       1. A sonic coupling between a sonic transducer and a wall of a conduit comprising: (a) means for forming a liquid-tight cavity between said sonic transducer and said wall of said conduit;   (b) a liquid having a substantially constant sound transmission temperature coefficient over a desired temperature range, said liquid substantially filling said means for forming a liquid-tight cavity;   (c) membrane means which normally seals said means for forming a liquid-tight cavity from the environment outside said means for forming a liquid-tight cavity; and   (d) hypodermic needle means for selectively adding said liquid to said means for forming a liquid-tight cavity and for removing gas from said means for forming a liquid-tight cavity by passing a portion of said hypodermic needle means through said membrane.   
     
     
       2. The sonic coupling of claim 1, wherein said liquid is a mixture of at least two component liquids, at least one of said component liquids having a sound transmission temperature coefficient opposite to the sound transmission temperature coefficients of the other component liquids, said component liquids mixed in proportions so that the sound transmission temperature coefficient of said liquid is substantially constant over a desired temperature range. 
     
     
       3. The sonic coupling of claim 1, wherein said means for forming a liquid-tight cavity comprises: cavity means having a shaped-portion which substantially conforms to said wall of said conduit; and   seal means arranged between said shaped-portion and said wall for providing a liquid-tight seal between said cavity means and said conduit.   
     
     
       4. The sonic coupling of claim 3, wherein said transducer is effectively sonicly connected to said liquid to said cavity means. 
     
     
       5. The sonic coupling of claim 3, wherein said seal means is resilient material attached to said shaped-portion for providing a seal when said cavity means is in compression with said conduit. 
     
     
       6. The sonic coupling of claim 1, further comprising expansion means within a portion of said means for forming a liquid-tight cavity for providing for expansion and contraction of the volume of said means for forming a liquid-tight cavity as the volume of said liquid changes with temperature. 
     
     
       7. The sonic coupling of claim 6, wherein said expansion means is a membrane. 
     
     
       8. The sonic coupling of claim 1, wherein said means for forming a liquid-tight cavity is wedge shaped. 
     
     
       9. The sonic coupling of claim 1, wherein said liquid absorbs sonic standing waves. 
     
     
       10. In a sonic flowmeter apparatus employing a transducer to measure the flow of a media in a conduit, an improved transducer means coupling comprising: (a) means for forming a liquid-tight cavity between a wall of said conduit and said transducer;   (b) a liquid having a substantially constant sound transmission temperature coefficient filling said means for forming a liquid-tight cavity; and   (c) means for inserting said liquid into said means for forming a liquid-tight cavity including membrane means which normally seals said cavity from the environment outside said cavity and hypodermic needle means for selectively adding said liquid to said means for forming a liquid-tight cavity or for removing gas from said means for forming a liquid-tight cavity by passing a portion of said hypodermic needle means through said membrane means.   
     
     
       11. The apparatus of claim 10, wherein said liquid is a mixture of component liquids having opposite sound transmission temperature coefficients, which component liquids are mixed in proportions so that the combined sound transmission temperature coefficient of said liquid is substantially the temperature range of said media. 
     
     
       12. The apparatus of claim 11, wherein said selected temperature range is substantially the temperature range of said media. 
     
     
       13. The apparatus of claim 10, wherein said liquid is a mixture of water having a positive sound transmission temperature coefficient and a liquid having a negative sound transmission temperature coefficient. 
     
     
       14. The apparatus of claim 10, wherein said means for forming a liquid-tight cavity comprises: a cavity having a shaped-portion which substantially conforms to said wall of said conduit; and   seal means disposed between said shaped-portion and said wall for providing a liquid-tight seal between said cavity and said conduit.   
     
     
       15. The apparatus of claim 14, wherein said cavity is connected to said transducer means and transmits sound between said transducer means and said liquid filling said cavity. 
     
     
       16. The apparatus of claim 14, wherein said seal means is a resilient material attached to said shaped-portion and forms a seal when said cavity is pressed against said wall of said conduit. 
     
     
       17. The apparatus of claim 10, further comprising expansion means within a wall of said means for forming a liquid-tight cavity for providing for expansion and contraction of the volume of said means for forming a liquid-tight cavity as the volume of said liquid changes with temperature. 
     
     
       18. The apparatus of claim 17, wherein said expansion means is a flexible membrane mounted in said wall. 
     
     
       19. A method of coupling transducer means of a sonic flowmeter apparatus to a conduit within which the flow of a media is to be measured, said method comprising the steps of: (a) providing a liquid-tight cavity between a wall of said conduit and said transducer means; and   (b) substantially filling said liquid-tight cavity with a liquid having a substantially constant sound transmission temperature coefficient by inserting a hypodermic needle through membrane means provided in a wall of said liquid-tight cavity.   
     
     
       20. The method of claim 19, wherein said liquid is a mixture of component liquids having opposite sound transmission temperature coefficients, which component liquids are mixed in proportions so that the combined sound transmission temperature coefficient of said liquid is substantially constant over a selected temperature range. 
     
     
       21. The method of claim 19, further including the step of providing for the escape of air from said cavity during the step of filling said liquid-tight cavity with fluid. 
     
     
       22. The method of claim 21 wherein said step of providing for the escape of air from said cavity is accomplished by inserting a hypodermic needle through a membrane providing in a wall of said liquid-tight cavity. 
     
     
       23. The method in accordance with claim 19, wherein said liquid-tight cavity is wedge shaped.